Blood vessels are cut during surgical procedures. Electrocautery is effectively used to reduce or stop hemorrhaging by “burning” the bleeding blood vessels, which seals them off. Various types, shapes, and sizes of tips (probes) are available for specific treatments. A small electrode is applied to the skin near the surgical site. This is used to collect the electricity from the body and safely discharge it back to the machine. A grounding pad is placed on the person's body (usually the thigh) before the surgery starts to protect the patient. Electrocautery prevents bleeding from small sized blood vessels and capillary beds. Larger blood vessels require temporary ligation during surgery.
There are two archetypical ways to achieve temporary ligation. The first way is to ligate from the outside of a blood vessel using clamps, clips and tourniquets or snares. Such devices press against opposite sides of a flexible hollow tube so that the walls flatten out and bear against one another. This produces an axially-extending fold at the two edges. For stopping the flow of fluid through the vessel, this squeezing or pinching action is very effective. However, the lumen of these vessels have linings (intima), which should not be traumatized by strong distortions. Strong pressures, and excessive bending (axial folding), can traumatize them leading to complications after the occluder is removed.
Surgical clamps exist in many sizes with many different types of clamp shapes (e.g., curved jaws, straight jaws, etc.). In addition, many different types of jaw surfaces exist, as adapted to the specific function performed by the clamp. When a different function is to be performed, either one must use a different clamp, or in some circumstances replaceable pads may be added to the jaws. Many existing surgical clamps have jaws with hard clamping surfaces. Some replaceable pads for these clamps are designed to fit over the jaws to provide a softer clamping surface. Vascular clamps, once they are clamped to the blood vessel, are usually held in the closed position manually by the operator, or with a locking mechanism.
Clamps and clips have some shortcomings in that atherosclerotic plaque in blood vessels and calcified blood vessels do not withstand the pressure exerted by these devices. It is well known that in crossclamping of the aorta for bypass operations, plaque may be released when the clamps are opened again and the plaques may lead to strokes (Boivie P, Hansson M, Engstrom K G. “Embolic material generated by multiple aortic crossclamping: a perfusion model with human cadaveric aorta.” J Thorac Cardiovasc Surg 2003 June; 125(6): 1451-60; van der Linden J, Hadjinikolaou L, Bergman P, Lindblom D. “Postoperative stroke in cardiac surgery is related to the location and extent of atherosclerotic disease in the ascending aorta.” J Am Coll Cardiol 2001 July; 38(1):131-5). In addition, especially in older patients, calcified blood vessels, when clamped, may lead to vessel damage.
A second way to achieve temporary ligation is to occlude the blood flow internally. In temporary ligation using for example balloon angioplasty, a deflated balloon catheter is placed at the arterial or venous site to be occluded; and then, the balloon is inflated, thereby blocking blood flow at the site. When the ligation is no longer necessary, the balloon may be deflated and the catheter removed (Matsuoka S, Uchiyama K, Shima H, Ohishi S, Nojiri Y, Ogata H. “Temporary percutaneous aortic balloon occlusion to enhance fluid resuscitation prior to definitive embolization of posttraumatic liver hemorrhage.” Cardiovasc Intervent Radiol 2001 July-August; 24(4):274-6; Joseph N, Levy E, Lipman S. “Angioplasty-related iliac artery rupture: treatment by temporary balloon occlusion.” Cardiovasc Intervent Radiol 1987; 10(5):276-9). However, the inflated balloon leads to dilation of the artery and the injury to the intima can lead to thickening and narrowing of the artery (Wainwright C L, Miller A M, Wadsworth R M. “Inflammation as a key event in the development of neointima following vascular balloon injury.” Clin Exp Pharmacol Physiol 2001 November; 28(11):891-5; Labropoulos N, Giannoukas A D, Volteas S K, al Kutoubi A. “Complications of the balloon assisted percutaneous transluminal angioplasty.” J Cardiovasc Surg (Torino) 1994 December; 35(6):475-89). Another way to internally occlude blood vessels is a “T” shaped device with a bulbous tip placed at either end of the “T.” These devices are manufactured from silicon rubber. The bulbous tips of the device are inserted into each of the two parts of the vessel. The bulbous tips have to be the right size to effectively occlude the blood vessel. Too large and the bulbs will damage the intima, too small and the bulbs do not efficiently occlude and stop blood flow. See e.g. U.S. Pat. Nos. 3,889,685; 4,168,708; 4,946,463. In clinical practice, these devices reduce bleeding at the arteriotomy, but do not stop bleeding. The surgeon, therefore, has still to rely on additional devices like misted blowers and suction devices to clear the surgical field of blood. Further, the surgeon has to take great care not to stitch through the device and be careful during removal of the device from the arteriotomy and not entangle the device in the suture.
Consequently, there is still a need for reversibly stopping blood flow during surgery, without damage or trauma occasioned by clamps or balloons. This holds great promise in terms of, for example, patient outcome.